The principal aim of this proposed pre-doctoral National Research Service Award (NRSA) application is to support the applicant's career goal of becoming an independent investigator leading a program of research to understand the genetic and environmental etiology of alcohol misuse and its intersection with internalizing (mood, anxiety disorders) and externalizing (antisocial behavior, illicit drug use) psychopathology. This aim will be achieved through the applicant's three-fold training goals: 1) obtaining phenotypic expertise in alcohol misuse (and related outcomes); 2) developing methodological skills to elucidate the complex nature of alcohol misuse and the internalizing and externalizing pathways leading to it; and 3) cultivating career and professional development skills. The proposed training plan centers on developing the applicant's scientific abilities through individualized mentorship, coursework, advanced statistical training, dissemination activities, and, principally, a statistical and molecular genetic study of alcohol misuse. Alcohol misuse, including binge drinking and pathological use, is widespread among college students, and it is associated with many negative public health outcomes. Despite substantial efforts, researchers have not been able to unequivocally elucidate the genetic and environmental factors underlying alcohol misuse. One explanation for this difficulty is that the phenotypic and underlying genetic architecture of alcohol misuse is heterogeneous - that is, alcohol misuse is not driven by a single set of genetic or environmental causes, but there may be many distinct sets of risk factors contributing to alcohol misuse that differ greatly between individuals. Motives for drinking (e.g. drinking to relieve negative emotions versus drinking to enhance positive emotions) have strong empirical associations with alcohol use behaviors and present a clear mechanism by which divergent genetic and environmental pathways may influence alcohol misuse. Negative and positive reinforcement drinking motives are related, respectively, to neuroticism and impulsivity, and mirror the schema of a prominent typology that categorizes internalizing versus externalizing alcoholics. The primary aim of this proposal is to utilize drinking motives to reduce phenotypic complexity and thereby investigate genetic and environmental factors contributing to diverging pathways to alcohol misuse, which we hypothesize correspond to internalizing and externalizing subtypes. To do this, we take advantage of data from a large (N = 9,890), longitudinal, prospective study of college students involving collection of both DNA samples and self-reported phenotypic data. This study design allows for investigation of biological, psychological, and social aspects of alcohol misuse across an important developmental period. There is a critical need to understand the diverse pathways that can lead individuals to risky or pathological alcohol use in order to alleviate the associated costly and harmful consequences.